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-rw-r--r--Documentation/block/queue-sysfs.txt10
-rw-r--r--block/blk-settings.c4
-rw-r--r--block/blk-sysfs.c40
-rw-r--r--include/linux/blkdev.h1
4 files changed, 53 insertions, 2 deletions
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index 3a29f89..e5d9148 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -20,7 +20,7 @@ This shows the size of internal allocation of the device in bytes, if
reported by the device. A value of '0' means device does not support
the discard functionality.
-discard_max_bytes (RO)
+discard_max_hw_bytes (RO)
----------------------
Devices that support discard functionality may have internal limits on
the number of bytes that can be trimmed or unmapped in a single operation.
@@ -29,6 +29,14 @@ number of bytes that can be discarded in a single operation. Discard
requests issued to the device must not exceed this limit. A discard_max_bytes
value of 0 means that the device does not support discard functionality.
+discard_max_bytes (RW)
+----------------------
+While discard_max_hw_bytes is the hardware limit for the device, this
+setting is the software limit. Some devices exhibit large latencies when
+large discards are issued, setting this value lower will make Linux issue
+smaller discards and potentially help reduce latencies induced by large
+discard operations.
+
discard_zeroes_data (RO)
------------------------
When read, this file will show if the discarded block are zeroed by the
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 12600bf..b38d8d7 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -116,6 +116,7 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->chunk_sectors = 0;
lim->max_write_same_sectors = 0;
lim->max_discard_sectors = 0;
+ lim->max_hw_discard_sectors = 0;
lim->discard_granularity = 0;
lim->discard_alignment = 0;
lim->discard_misaligned = 0;
@@ -303,6 +304,7 @@ EXPORT_SYMBOL(blk_queue_chunk_sectors);
void blk_queue_max_discard_sectors(struct request_queue *q,
unsigned int max_discard_sectors)
{
+ q->limits.max_hw_discard_sectors = max_discard_sectors;
q->limits.max_discard_sectors = max_discard_sectors;
}
EXPORT_SYMBOL(blk_queue_max_discard_sectors);
@@ -641,6 +643,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
b->max_discard_sectors);
+ t->max_hw_discard_sectors = min_not_zero(t->max_hw_discard_sectors,
+ b->max_hw_discard_sectors);
t->discard_granularity = max(t->discard_granularity,
b->discard_granularity);
t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) %
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 6264b38..b1f34e4 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -145,12 +145,43 @@ static ssize_t queue_discard_granularity_show(struct request_queue *q, char *pag
return queue_var_show(q->limits.discard_granularity, page);
}
+static ssize_t queue_discard_max_hw_show(struct request_queue *q, char *page)
+{
+ unsigned long long val;
+
+ val = q->limits.max_hw_discard_sectors << 9;
+ return sprintf(page, "%llu\n", val);
+}
+
static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
{
return sprintf(page, "%llu\n",
(unsigned long long)q->limits.max_discard_sectors << 9);
}
+static ssize_t queue_discard_max_store(struct request_queue *q,
+ const char *page, size_t count)
+{
+ unsigned long max_discard;
+ ssize_t ret = queue_var_store(&max_discard, page, count);
+
+ if (ret < 0)
+ return ret;
+
+ if (max_discard & (q->limits.discard_granularity - 1))
+ return -EINVAL;
+
+ max_discard >>= 9;
+ if (max_discard > UINT_MAX)
+ return -EINVAL;
+
+ if (max_discard > q->limits.max_hw_discard_sectors)
+ max_discard = q->limits.max_hw_discard_sectors;
+
+ q->limits.max_discard_sectors = max_discard;
+ return ret;
+}
+
static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *page)
{
return queue_var_show(queue_discard_zeroes_data(q), page);
@@ -360,9 +391,15 @@ static struct queue_sysfs_entry queue_discard_granularity_entry = {
.show = queue_discard_granularity_show,
};
+static struct queue_sysfs_entry queue_discard_max_hw_entry = {
+ .attr = {.name = "discard_max_hw_bytes", .mode = S_IRUGO },
+ .show = queue_discard_max_hw_show,
+};
+
static struct queue_sysfs_entry queue_discard_max_entry = {
- .attr = {.name = "discard_max_bytes", .mode = S_IRUGO },
+ .attr = {.name = "discard_max_bytes", .mode = S_IRUGO | S_IWUSR },
.show = queue_discard_max_show,
+ .store = queue_discard_max_store,
};
static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
@@ -421,6 +458,7 @@ static struct attribute *default_attrs[] = {
&queue_io_opt_entry.attr,
&queue_discard_granularity_entry.attr,
&queue_discard_max_entry.attr,
+ &queue_discard_max_hw_entry.attr,
&queue_discard_zeroes_data_entry.attr,
&queue_write_same_max_entry.attr,
&queue_nonrot_entry.attr,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d4068c1..243f29e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -268,6 +268,7 @@ struct queue_limits {
unsigned int io_min;
unsigned int io_opt;
unsigned int max_discard_sectors;
+ unsigned int max_hw_discard_sectors;
unsigned int max_write_same_sectors;
unsigned int discard_granularity;
unsigned int discard_alignment;
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